# Claude 2.1 vs Claude Sonnet 4.5

> Claude Sonnet 4.5 is the stronger model overall, scoring 44.1 to 25.2 on the Noometry Index.

- Canonical page: https://noometry.com/compare/claude-2-1-vs-claude-sonnet-4-5
- Last updated: 2026-10-12
- Shared benchmarks: 6

## Summary

- They share 6 benchmarks with published results for both. Claude 2.1 scores higher in 0 categories and Claude Sonnet 4.5 in 4 categories; 4 gaps are clear of the uncertainty.
- The widest gap is in knowledge, where Claude Sonnet 4.5 leads 48.4 to 15.4.
- The biggest single-benchmark swing is OTIS Mock AIME 2024-2025: 1.9% for Claude 2.1 and 77.8% for Claude Sonnet 4.5.

## Snapshot

| | Claude 2.1 | Claude Sonnet 4.5 |
|---|---|---|
| Provider | Anthropic | Anthropic |
| Noometry Index | 25.2 | 44.1 |
| Rank | 345 | 81 |
| Context | — | 200K |
| Input $/M | — | $3 |
| Output $/M | — | $15 |
| Weights | Proprietary | Proprietary |

## Coding

- Claude 2.1: 26.2 (#327)
- Claude Sonnet 4.5: 47.3 (#61)

| Benchmark | Claude 2.1 | Claude Sonnet 4.5 |
|---|---|---|
| WeirdML | 7.1% | 47.7% |
| SWE-bench Verified | — | 71.3% |
| SWE-bench Verified (bash only) | — | 71.4% |
| LMArena WebDev | — | 1393 |
| SWE-bench Multilingual | — | 67% |
| SciCode | — | 44.7% |
| GSO | — | 14.7% |
| LMArena Coding | — | 1489 |
| ALE-Bench | — | 796.15 |
| AlgoTune | — | 1.52 |

## Agentic & Tool Use

- Claude 2.1: —
- Claude Sonnet 4.5: 38.3 (#32)

| Benchmark | Claude 2.1 | Claude Sonnet 4.5 |
|---|---|---|
| Terminal-Bench | — | 46.5% |
| Berkeley Function Calling Leaderboard | — | 73.2% |
| GDPval | — | 42.5% |
| Remote Labor Index | — | 2.1% |
| τ²-bench Airline | — | 72% |
| τ²-bench Banking | — | 25.3% |
| τ²-bench Retail | — | 72.4% |
| τ²-bench Telecom | — | 84.9% |
| Cybench | — | 60% |
| DeepResearch Bench | — | 52.6% |
| OSWorld | — | 62.9% |
| LMArena Search | — | 1159 |
| METR Time Horizons | — | 67.4% |
| Vending-Bench 2 | — | 3,839 |

## Reasoning

- Claude 2.1: 21.4 (#221)
- Claude Sonnet 4.5: 26.9 (#125)

| Benchmark | Claude 2.1 | Claude Sonnet 4.5 |
|---|---|---|
| DTBench | 51% | 83.2% |
| Epoch Capabilities Index | 119.27 | 146.84 |
| ForecastBench | 54.2 | 61.9 |
| ARC-AGI-2 | — | 13.6% |
| SimpleBench | — | 54.3% |
| Kagi LLM Benchmark | — | 57.9% |
| NYT Connections (extended) | — | 37.3% |
| ARC-AGI-1 | — | 63.7% |
| CritPt | — | 1.1% |
| Chess Puzzles | — | 12% |
| EnigmaEval | — | 6% |
| EBR-Bench | — | 2.4% |
| LMArena Hard Prompts | — | 1462 |
| Mystery Game Puzzles | — | 17% |
| LMCA | — | 38.8% |

## Math

- Claude 2.1: 10.2 (#315)
- Claude Sonnet 4.5: 32.3 (#216)

| Benchmark | Claude 2.1 | Claude Sonnet 4.5 |
|---|---|---|
| OTIS Mock AIME 2024-2025 | 1.9% | 77.8% |
| FrontierMath (Tiers 1-3) | — | 23.9% |
| FrontierMath Tier 4 | — | 2.4% |
| ProofBench | — | 19% |
| Omni-MATH | — | 55.3% |
| LMArena Math | — | 1449 |
| MATH Level 5 | — | 97.7% |
| FrontierMath (Feb 2025 set) | — | 15.2% |
| FrontierMath Tier 4 (v1) | — | 4.2% |

## Knowledge

- Claude 2.1: 15.4 (#292)
- Claude Sonnet 4.5: 48.4 (#76)

| Benchmark | Claude 2.1 | Claude Sonnet 4.5 |
|---|---|---|
| GPQA Diamond | 33% | 82.3% |
| Humanity's Last Exam | — | 13.7% |
| SimpleQA Verified | — | 30.7% |
| MMLU-Pro | — | 86.9% |
| Vectara Hallucination Rate | — | 12% |
| GPQA (HELM) | — | 68.6% |
| LMArena Expert | — | 1482 |
| MMLU | 73.5% | — |

## Multimodal

- Claude 2.1: —
- Claude Sonnet 4.5: 34.8 (#89)

| Benchmark | Claude 2.1 | Claude Sonnet 4.5 |
|---|---|---|
| VPCT | — | 39.8% |
| LMArena Document | — | 1450 |

## Multilingual

- Claude 2.1: —
- Claude Sonnet 4.5: 53.4 (#69)

| Benchmark | Claude 2.1 | Claude Sonnet 4.5 |
|---|---|---|
| LMArena Non-English | — | 1425 |
| LMArena Chinese | — | 1459 |
| LMArena French | — | 1458 |
| LMArena German | — | 1427 |
| LMArena Japanese | — | 1390 |
| LMArena Korean | — | 1403 |
| LMArena Russian | — | 1437 |
| LMArena Spanish | — | 1457 |

## Instruction Following

- Claude 2.1: —
- Claude Sonnet 4.5: 75.0 (#78)

| Benchmark | Claude 2.1 | Claude Sonnet 4.5 |
|---|---|---|
| IFEval | — | 85% |
| LMArena Instruction Following | — | 1459 |

## Long Context

- Claude 2.1: —
- Claude Sonnet 4.5: 45.2 (#46)

| Benchmark | Claude 2.1 | Claude Sonnet 4.5 |
|---|---|---|
| LMArena Longer Query | — | 1476 |

## Writing & Preference

- Claude 2.1: —
- Claude Sonnet 4.5: 66.5 (#34)

| Benchmark | Claude 2.1 | Claude Sonnet 4.5 |
|---|---|---|
| LMArena Text | — | 1439 |
| LMArena Creative Writing | — | 1442 |
| EQ-Bench Creative Writing | — | 1678 |
| WildBench | — | 85.4% |
| LMArena Multi-Turn | — | 1465 |

## FAQ

### Is Claude 2.1 better than Claude Sonnet 4.5?

Claude Sonnet 4.5 is the stronger model overall, scoring 44.1 to 25.2 on the Noometry Index.

### Is Claude 2.1 or Claude Sonnet 4.5 better for coding?

Claude Sonnet 4.5 scores higher on coding benchmarks: 47.3 versus 26.2 in the Noometry coding category.

### How many benchmarks do Claude 2.1 and Claude Sonnet 4.5 share?

6 benchmarks have published results for both models. Claude 2.1 has 7 scored results on Noometry and Claude Sonnet 4.5 has 73.